This invention relates to a method and system for polling a large number of security system modules interconnected on a bus with a control panel in groups so as to reduce the overall polling time.
Security systems that comprise a number of devices, or modules, interconnected to a control panel by a communications bus, are well known in the art. Security modules typically are used to monitor an area of space or a specific access point, and report to the control panel if there is a change in status. For example, modules exist that monitor opening of doors or windows, that determine if an intruder has entered the premises such as by passive infrared surveillance techniques, or that determine if a fire has started, etc. Since most of these types of devices only report changes in status when a triggering event occurs, and a triggering event such as a fire may never in fact occur, it is important to poll or query each module on some periodic basis in order to ensure that they are up and running. This polling process is referred to as supervision of the modules, and generally is carried out by the control panel querying each module individually to determine at least if it is capable of sending a response back to the panel. If any given module does not report back, then the system will provide a warning to the system operator or monitoring company that the module needs to be investigated.
In present security systems which employ unique serial number addressing for each module, the minimum time required to unit poll a single module in the system is a function of how many bits at, say 1 Kbaud, are contained in the unit poll message. This can be as much as 50 ms for a 37-bit unit poll including the required time of an inter-poll delay. Unit polls are required to supervise, or interrogate the proper functioning, of every module in the system. In a system containing 250 modules, it will take (50 ms)(250)=12.5 sec for the control panel to supervise every module in that system. If any one of the modules become inoperative (non-responsive to the unit poll) it would take the control panel an average of 12.5/2=6.25 sec and a maximum of 12.5 seconds to identify and report that defective module to the user and/or the monitoring company""s central station.
In certain applications, this polling time is unacceptable. For example, in Europe, defective modules are required to be identified and reported in less than 2-4 seconds. It is anticipated that such a requirement will eventually become a domestic requirement once it has been demonstrated that fast polling systems exceeding 9600 baud are common place. It is therefore desired to be able to effect a poll of a substantially large number of modules in a relatively shorter amount of time, that is, to be more efficient than the prior art sequential unit poll scenario currently being implemented.
This invention reduces the supervision time by a substantial factor via unique group supervision polling. In the preferred embodiment below, the maximum supervision time is reduced by a factor of 16 (from 12.8 seconds to 12.8/16=0.8 second, reducing the average supervision time to only 0.4 second). This is accomplished in a security system that has a large number of individually-addressable modules interconnected on a data bus to a control panel by a method of concurrently supervising the modules by first configuring each module with a unique zone number correlated to a group number and a module number. During operation, the control panel initiates a group supervision poll sequence for each group of modules by transmitting a group poll command including a group number data field, with the group number data field being populated by the group of modules currently being polled. Each module responds to the group poll command by first determining if it is a member of the group currently being polled by comparing the group number data field to the group number portion of the zone number with which it has been previously configured. For each module that is a member of the group being polled, a discrete bit is set in a group poll response message that logically corresponds to the module number for that module. The control panel then determines if any bit in the group poll response message has not been set, and then issues a unit poll sequence addressed to a module that corresponds to any such bit not determined to have been set in the group poll response message.
Each module may be configured with a unique zone number by first logically dividing the plurality of modules into n groups of modules, then assigning a group number to each group of modules and assigning a module number to each module within a group. The control panel transmits to each module a data string including a zone number, with the zone number assembled from the group number and the module number assigned to that module, and the zone number is stored by each module for later use. Each module is individually addressable by a unique serial number that was previously stored therein.
For example, the zone number may be an eight-bit data word comprised of a four-bit group number and a four-bit module number.